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Installing Windows

A membrane goes over the rough sill before the window is installed and the nailing flange gets nailed through that. This will allow any water that may get trapped a way out.
Somebody correct me if I'm wrong but I think the only flange that gets covered with a membrane is the top of the window.

Installing Windows

Installing Windows

Quote:

Originally Posted by sandyman720

So put it on the tyvek around the windows?

See this Tyvek document. Look at page 6 and they illustrate the sealant going around the perimeter of the rough opening and there's also some flashing details. One point of contradiction though... Dupont says not to apply sealant across the bottom sill flange. Anderson window installation instructions says you do. I would refer to the recommendations of your window manufacturer for the specific instructions on this. Not knowing who's windows you are using I went on the Anderson guidelines.

Installing Windows

Clutchcargo -

Maybe the This Old House is one factor in the rediculous number of improperly installed windows (estimated at 60-70%). Unfortunately, you do not know they are improperly installed until it is a few years too late.

For those that are interested, there is a program to become a certified window installer. Some builders will only sub out to certified installers or they invest the time and money to get their own people trained and certified. The certification class is supported by the window manufacturers and is provided for a fee ($300-$400??? when i took it) by independent construction oriented firms.

Installing Windows

Here's a picture of how not to flash. It's a beaut ain't it? Tyvek ripped, top of the window flashing all crumbled up, sheathing exposed. Boys, it's hard to find good help these days.

They covered the rough sill, then covered the left and right trimmers, installed the window, then put the last piece over the top flange. Maybe there was some other reason they did it that way. They were using the pre-fabricated panel construction. It looked like they didn't use a house wrap on that portion as well.

Quote:

Originally Posted by concretemasonry

Clutchcargo -
Unfortunately, you do not know they are improperly installed until it is a few years too late.